The present invention relates to fluid pressure driven clamps and particularly to such clamps which include an extendable clamping member.
Extending clamps generally comprise a clamping member which can be moved away from a clamping area and which can return to the clamping area to apply clamping forces to an object placed in the clamping area. Such clamps are useful in present day industrial environments, particularly where successive parts are to be appropriately placed before the clamp and then clamped. It is desirable to have a clamp with a relatively long extension which can apply large clamping forces with minimum power required both for extension and clamping. These goals have not been achieved with known clamps. Clamps which are capable of large clamping forces tend to be physically large and have limited extension. Conversely, clamps which have long possible extension typically are not capable of large clamping forces.
These limitations in prior extending clamps are overcome in accordance with the embodiments herein which describe a compact extending clamp capable of relatively long extension and large clamping forces. The clamp of the embodiment includes a main clamping block which incorporates most of the active parts of the extending clamp assembly. The main block is pivotably mounted to a stationary mounting plate which is affixed to a surface against which clamping is to occur. The main block of the embodiment is constructed of a solid metal block into which openings are formed to convey control fluids and to retain the moving parts of the assembly. The clamping end of the main block is referred to as the outward end. A pressure cylinder is disposed within the moving block at the other end, called the inward end, of the main block so that the pivoting of the main block results in a seesaw motion of the inward and outward ends of the main block. The clamping cylinder may, for example, be a hydraulic cylinder which receives fluid under pressure from an inlet at the inward end of the main block. Advantageously, the clamping cylinder is disposed near the pivot at an outward angle to increase the lever arm available for clamping forces. The outward end of the main block is raised in the absence of hydraulic pressure in the cylinder by a spring on the outward side of the pivot.
The clamping forces are applied to objects to be clamped by the clamping rod which is slidably disposed within the main block. The clamping rod in its retracted state extends from the outward end of the main block, crossing above the pivot and ending on the inward side of the pivot. An air cylinder is disposed within the main block to extend the clamping rod by means of compressed air applied at an inlet connected to the inward end of the main block. The clamping rod has a slot along its length which, in conjunction with a retaining member of the main block performs a number of significant functions. The retaining member extends through the slot in sliding contact therewith. An outward end of the slot contacts the retaining member to define the maximum retraction of the clamping rod. Similarly, an inward end of the slot contacts the retaining member to define the maximum extension of the clamping rod. The retaining member, by extending through the slot also serves to keep the clamping rod from rotating and thus keeps the clamping surface of the clamping rod in a downward position. Advantageously, the embodiment shows a clamping rod retraction spring disposed within a central bore formed within the clamping rod. The spring provides retraction forces by urging against an inward end of the clamping rod bore and against the retaining member.